Optical semiconductor element and optical semiconductor device

ABSTRACT

An optical semiconductor device includes an optical semiconductor element, a metal pattern and at least one thermal conductive material. The optical semiconductor element has a first optical waveguide region and a second optical waveguide region. The second optical waveguide region is optically coupled to the first optical waveguide region and has a heater for changing a refractive index of the second optical waveguide region. The metal pattern is provided on an area to be thermally coupled to a temperature control device. The thermal conductive material couples the metal pattern with an upper face of the first optical waveguide region of the optical semiconductor element. The thermal conductive material is electrically separated from the first optical waveguide region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of application Ser. No. 12/314,350,filed Dec. 9, 2009, which is a Divisional application of U.S. patentapplication Ser. No. 11/730,260, filed Mar. 30, 2007, now U.S. Pat. No.7,474,684, issued Jan. 6, 2009, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to an optical semiconductor element andan optical semiconductor device.

2. Description of the Related Art

Generally, a wavelength-tunable semiconductor laser has a gain for alaser emission and can select a wavelength of the laser. There are somemethods of selecting a wavelength. For example, the methods include amethod of changing a resonant wavelength of loss or gain by changing arefractive index or angle of a diffractive grating or an etalon providedin a laser cavity. And the methods include a method of changing aresonant wavelength of the laser cavity by changing an optical length inthe laser cavity (refractive index or a physical length of the lasercavity).

The method of changing the refractive index has an advantage inreliability or manufacturing cost, because a mechanical operatingportion is not necessary being different from the method of changing theangle or length. The refractive index changing method includes changinga temperature of an optical waveguide, changing a carrier density in theoptical waveguide by providing a current, and so on. A semiconductorlaser having a Sampled Grating

Distributed Reflector (SG-DR) is supposed as a wavelength tunablesemiconductor laser that changes a temperature of an optical waveguide,where the SG-DR has a wavelength selection function.

In this semiconductor laser, if a reflection spectrum of a plurality ofSG-DR regions (reflection region) is controlled preferably, apredetermined wavelength can be selected with a vernier effect. That is,this semiconductor laser emits a laser at a wavelength where reflectionpeaks of two SG-DR regions are overlapped with each other. It istherefore possible to select the lasing wavelength by controlling eachof the reflection peaks of the SG-DR regions.

Generally, a heater is provided on a surface of one of the SG-DRregions. It is possible to change the temperature of an opticalwaveguide of the SG-DR region where the heater is provided, with heatgenerated by the heater. As a result, a refractive index of the opticalwaveguide is changed. Accordingly, it is possible to select a reflectionpeak wavelength of the SG-DR region where the heater is provided, bycontrolling the heating value of the heater.

And it is possible to control the lasing wavelength to be a desirableone by controlling the refractive index of the optical waveguide of theSG-DR segments, with use of a temperature control device providing heatto whole of a semiconductor laser. And so, Japanese Patent ApplicationPublication No. 9-92934 (hereinafter referred to as Document 1)discloses a method of controlling a lasing wavelength of thesemiconductor laser by providing an electrical power to a heater and atemperature control device separately.

However, it is apprehended that the temperature of an SG-DR region nothaving a heater is changed, when heating value of the heater is large.In this case, the lasing wavelength is off from a desirable one. In thesemiconductor laser disclosed in Document 1, an active region (a gainregion) and a DBR region (a reflecting region) having a heater areadjacent to each other. As is the case of the conventional art, if theheating value of the heater is large, the temperature of the activeregion not having the heater is changed. Therefore, the lasingwavelength is off from a desirable one in the semiconductor laserdisclosed in Document 1.

SUMMARY OF THE INVENTION

The present invention provides an optical semiconductor element and anoptical semiconductor device that can control a lasing wavelengthaccurately.

According to an aspect of the present invention, preferably, there isprovided an optical semiconductor device including an opticalsemiconductor element, a metal pattern and at least one thermalconductive material. The optical semiconductor element has a firstoptical waveguide region and a second optical waveguide region. Thesecond optical waveguide region is optically coupled to the firstoptical waveguide region and has a heater for changing a refractiveindex of the second optical waveguide region. The metal pattern isprovided on an area to be thermally coupled to a temperature controldevice. The thermal conductive material couples the metal pattern withan upper face of the first optical waveguide region of the opticalsemiconductor element. The thermal conductive material is electricallyseparated from the first optical waveguide region.

With the above-mentioned configuration, heat is conducted to the firstoptical waveguide region through the thermal conductive material fromthe metal pattern that is provided on the area to be thermally coupledto the temperature control device. In this case, the first opticalwaveguide region is heated from a connecting point with the thermalconductive material and from the area to be thermally coupled to thetemperature control device. It is therefore possible to control thetemperature of the first optical waveguide region effectively in theoptical semiconductor device, being less subjected to the heat of theheater. Accordingly, it is possible to control a lasing wavelength.

According to another aspect of the present invention, preferably, thereis provided an optical semiconductor device including an opticalsemiconductor element, a metal pattern and at least one thermalconductive material. The optical semiconductor element has a firstoptical waveguide region and a second optical waveguide region. Thesecond optical waveguide region is optically coupled to the firstoptical waveguide region and has a heater for changing a refractiveindex of the second optical waveguide region. The metal pattern isprovided on an area to be thermally coupled to a temperature controldevice. The thermal conductive material couples the metal pattern withan upper face of the first optical waveguide region of the opticalsemiconductor element. The thermal conductive material is electricallycoupled to the first optical waveguide region.

With the above-mentioned configuration, heat is conducted to the firstoptical waveguide region through the thermal conductive material fromthe metal pattern that is provided on the area to be thermally coupledto the temperature control device. In this case, the first opticalwaveguide region is heated from a connecting point with the thermalconductive material and from the area to be thermally coupled to thetemperature control device. It is therefore possible to control thetemperature of the first optical waveguide region effectively in theoptical semiconductor device, being less subjected to the heat of theheater. Accordingly, it is possible to control a lasing wavelength.

According to another aspect of the present invention, preferably, thereis provided an optical semiconductor device including an opticalsemiconductor element, a metal pattern and a plurality of thermalconductive material. The optical semiconductor element has a firstoptical waveguide region and a second optical waveguide region. Thesecond optical waveguide region is optically coupled to the firstoptical waveguide region and has a heater for changing a refractiveindex of the second optical waveguide region. The metal pattern isprovided on an area to be thermally coupled to a temperature controldevice. The thermal conductive material couples the metal pattern withan upper face of the first optical waveguide region of the opticalsemiconductor element. The thermal conductive material is electricallycoupled to the first optical waveguide region.

With the above-mentioned configuration, heat is conducted to the firstoptical waveguide region through the thermal conductive material fromthe metal pattern that is provided on the area to be thermally coupledto the temperature control device. In this case, the first opticalwaveguide region is heated from a connecting point with the thermalconductive material and from the area to be thermally coupled to thetemperature control device. It is therefore possible to control thetemperature of the first optical waveguide region effectively in theoptical semiconductor device, being less subjected to the heat of theheater. Accordingly, it is possible to control a lasing wavelength.

According to another aspect of the present invention, preferably, thereis provided an optical semiconductor device including an opticalsemiconductor element, a metal pattern and at least one thermalconductive material. The optical semiconductor element has a firstoptical waveguide region and a second optical waveguide region. Thesecond optical waveguide region is optically coupled to the firstoptical waveguide region and has a heater for changing a refractiveindex of the second optical waveguide region. The metal pattern isprovided on an area to be thermally coupled to a temperature controldevice. The thermal conductive material couples the metal pattern withan upper face of the first optical waveguide region of the opticalsemiconductor element. The thermal conductive material is at the secondoptical waveguide region side with respect to a center of the firstoptical waveguide region.

With the above-mentioned configuration, heat is conducted to the firstoptical waveguide region through the thermal conductive material fromthe metal pattern that is provided on the area to be thermally coupledto the temperature control device. In this case, the first opticalwaveguide region is heated from a connecting point with the thermalconductive material and from the area to be thermally coupled to thetemperature control device. It is therefore possible to control thetemperature of the first optical waveguide region effectively in theoptical semiconductor device, being less subjected to the heat of theheater. Accordingly, it is possible to control a lasing wavelength.

According to another aspect of the present invention, preferably, thereis provided an optical semiconductor element including a first opticalwaveguide region, a second optical waveguide region and a metal pattern.The second optical waveguide region is optically coupled to the firstoptical waveguide region and has a heater for changing a refractiveindex of the second optical waveguide region. The metal pattern isprovided on an upper face of the first optical waveguide region and hasa length larger than half of that of the first optical waveguide regionin an optical axis direction of the first optical waveguide region.

With the above-mentioned configuration, heat is conducted to the firstoptical waveguide region from a heating portion such as a temperaturecontrol device when the metal pattern is thermally coupled to theheating portion. In this case, the first optical waveguide region isheated from the connecting points and the heating portion. It istherefore possible to control the temperature of the first opticalwaveguide region effectively in the optical semiconductor element, beingless subjected to the heat of the heater. Accordingly, it is possible tocontrol a lasing wavelength accurately. In addition, it is possible toconduct heat to the first optical waveguide region effectively becausethe metal pattern has a large length.

According to another aspect of the present invention, preferably, thereis provided an optical semiconductor element including a first opticalwaveguide region, a second optical waveguide region and a metal pattern.The second optical waveguide region is optically coupled to the firstoptical waveguide region and has a heater for changing a refractiveindex of the second optical waveguide region. The metal pattern isprovided on an upper face of the first optical waveguide region at thesecond optical waveguide region side with respect to a center of thefirst optical waveguide region.

With the above-mentioned configuration, heat is conducted to the firstoptical waveguide region from a heating portion such as a temperaturecontrol device when the metal pattern is thermally coupled to theheating portion. In this case, the first optical waveguide region isheated from the connecting points and the heating portion. It istherefore possible to control the temperature of the first opticalwaveguide region effectively in the optical semiconductor element, beingless subjected to the heat of the heater. Accordingly, it is possible tocontrol a lasing wavelength accurately. In addition, it is possible tocontrol the temperature of an area of the first optical waveguide regionsubjected to the heat of the heater.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail with reference to the following drawings, wherein:

FIG. 1A and FIG. 1B illustrate a laser module in accordance with a firstembodiment of the present invention;

FIG. 2 illustrates an overall structure of a laser module in accordancewith a second embodiment of the present invention;

FIG. 3 illustrates an overall structure of a laser module in accordancewith a third embodiment of the present invention;

FIG. 4 illustrates an overall structure of a laser module in accordancewith a fourth embodiment of the present invention;

FIG. 5 illustrates an overall structure of a laser module in accordancewith a fifth embodiment of the present invention;

FIG. 6 illustrates an overall structure of a laser module in accordancewith a sixth embodiment of the present invention;

FIG. 7 illustrates an overall structure of a laser module in accordancewith a seventh embodiment of the present invention; and

FIG. 8 illustrates an example where the present invention is applied toanother optical semiconductor element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given, with reference to the accompanyingdrawings, of embodiments of the present invention.

First Embodiment

FIG. 1A and FIG. 1B illustrate a laser module 100 in accordance with afirst embodiment of the present invention. FIG. 1A illustrates a topview of the laser module 100. FIG. 1B illustrates a cross sectional viewtaken along a line A-A of FIG. 1A. As shown in FIG. 1A, the laser module100 has a temperature control device 20, a mount carrier 30 and awavelength-tunable semiconductor laser chip 40. The mount carrier 30 maybe a heat sink, a subcarrier, a submount or the like. A controller 200and an electrical power supply 300 are provided out of the laser module100. The controller 200 controls an operation of the laser module 100.The electrical power supply provides an electrical power to the lasermodule 100. The controller 200 has a central processing unit (CPU), aread only memory (ROM), a random access memory (RAM) and so on. Thelaser module 100, the controller 200 and the electrical power supply 300are collectively referred to as a laser device.

The temperature control device 20 controls the temperature of thewavelength-tunable semiconductor laser chip 40. The temperature controldevice 20 is coupled to the electrical power supply 300 through acontrol terminal or the like (not shown). The temperature control device20 controls the temperature of the wavelength-tunable semiconductorlaser chip 40 by changing the temperature of the surface thereofaccording to an electrical power provided from the electrical powersupply 300. The mount carrier 30 is mounted on the temperature controldevice 20. An electrode 31 and the wavelength-tunable semiconductorlaser chip 40 are mounted on the mount carrier 30.

The electrode 31 is a metal pattern composed of a metal such as Au. Anelectrode 8 of the wavelength-tunable semiconductor laser chip 40 andthe electrode 31 are coupled to each other with a plurality of wires 32.The wire 32 is composed of a metal such as Au. The wire 32 has adiameter of approximately 20 μm. The electrode 31 is coupled to theelectrical power supply 300 through a control terminal or the like (notshown).

As shown in FIG. 1B, the wavelength-tunable semiconductor laser chip 40has a structure in which a Sampled Grating Distributed Reflector (SG-DR)region A, a Sampled Grating Distributed Feedback (SG-DFB) region B and aPower Control (PC) region C are coupled in order.

The SG-DR region A has a structure in which an optical waveguide layer3, a cladding layer 5 and an insulating layer 6 are laminated on asubstrate 1 in order and a heater 9, a power electrode 10 and a groundelectrode 11 are laminated on the insulating layer 6. The SG-DFB regionB has a structure in which an optical waveguide layer 4, the claddinglayer 5, a contact layer 7 and the electrode 8 are laminated on thesubstrate 1 in order. The PC region C has a structure in which anoptical waveguide layer 12, the cladding layer 5, a contact layer 13 andan electrode 14 are laminated on the substrate 1 in order. The substrate1 and the cladding layer 5 of the SG-DR region A, the SG-DFB region Band the PC region C are a single layer formed as a unit respectively.The optical waveguide layers 3, 4 and 12 are formed on a same plane andare optically coupled to each other.

A low reflecting coating 15 is formed on end facet of the substrate 1,the optical waveguide layer 3 and the cladding layer 5 at the SG-DRregion A side. On the other hand, a low reflecting coating 16 is formedon end facet of the substrate 1, the optical waveguide layer 12 and thecladding layer 5 at the PC region C side. Diffractive gratings 2 areformed at an interval in the optical waveguide layers 3 and 4. Thesampled grating is thus formed. The insulating layer 6 is further formedbetween the electrode 8 and the electrode 14.

The substrate 1 is, for example, a semiconductor substrate composed ofInP. The optical waveguide layer 3 is, for example, composed of InGaAsPcrystal having an absorption edge wavelength at shorter wavelengths sidecompared to the lasing wavelength. PL wavelength of the opticalwaveguide layer 3 is approximately 1.3 μm. The optical waveguide layer 4is, for example, an active layer composed of InGaAsP crystal foramplifying a light of a desirable wavelength of a laser emission. The PLwavelength of the optical waveguide layer 4 is approximately 1.57 μm.The optical waveguide layer 12 is, for example, composed of InGaAsPcrystal for changing the output of the emitted light by absorbing oramplifying a light. The PL wavelength of the optical waveguide layer 12is approximately 1.57 μm.

SG-DR segments are formed in the optical waveguide layer 3. Other SG-DRsegments are formed in the optical waveguide layer 4. Three SG-DRsegments are formed in the optical waveguide layer 3 and in the opticalwaveguide layer 4 respectively, in the embodiment. Here, the SG-DRsegment is a region in which one region having the diffractive grating 2and one space region not having the diffractive grating 2 are combinedin the optical waveguide layers 3 and 4.

The cladding layer 5 is composed of InP. The cladding layer 5 confines alaser light traveling in the optical waveguide layers 3, 4 and 12. Thecontact layers 7 and 13 are composed of InGaAsP crystal. The insulatinglayer 6 is a passivation film composed of an insulator such as SiN. Thelow reflecting coatings 15 and 16 are, for example, composed of adielectric film including MgF₂ and TiON. The reflectivity of the lowreflecting coatings 15 and 16 are, for example, less than 0.3%.

The heater 9 is composed of such as NiCr and is provided above the SG-DRsegment of the optical waveguide layer 3. The power electrode 10 and theground electrode 11 are coupled to the heater 9. The power electrode 10,the ground electrode 11, the electrode 8 and the electrode 14 arecomposed of a conductive material such as Au. The power electrode 10 andthe electrode 14 are coupled to the electrical power supply 300 througha control terminal or the like (not shown).

Next, a description will be given of a controlling method of the lasermodule 100. At first, the controller 200 controls the electrical powersupply 300 so that a current is provided to the electrode 8 through theelectrode 31 and the wires 32. A light is generated in the opticalwaveguide layer 4. And the controller 200 controls the electrical powersupply 300 so that a current is provided to the electrode 14. The lightpropagates in the optical waveguide layers 3 and 4, and is reflected andamplified repeatedly. Then, it causes lasing oscillation. A part of theemitted light is amplified or absorbed in the optical waveguide layer 12and is emitted through the low reflecting coating 16. It is possible tocontrol the gain or the absorptance of the optical waveguide layer 12with the current provided to the electrode 14. The controller 200 cankeep the output of the emitted light of the wavelength-tunablesemiconductor laser chip 40 constant by controlling the current to beprovided to the electrode 14.

The controller 200 controls the electrical power supply 300 so that acurrent is provided to the heater 9. The controller 200 can control thetemperature of the SG-DR segment of the SG-DR region A according to thecurrent to be provided to the heater 9. In this case, the refractiveindex of the SG-segment of the SG-DR region A is changed. And areflection peak wavelength of the optical waveguide layer 3 is changed.Accordingly, a laser light is emitted at a wavelength where thereflection peak wavelength of the SG-DR region A and the reflection peakwavelength of the SG-DFB region B are overlapped to each other. That is,it is possible to select a lasing wavelength of the wavelength-tunablesemiconductor laser chip 40.

The controller 200 controls the electrical power supply 300 so that acurrent is provided to the temperature control device 20. The controller200 can control both temperatures of the optical waveguide layer 3 andthe optical waveguide layer 4 according to the current to be provided tothe temperature control device 20. In this case, the refractive index ofthe optical waveguide layers 3 and 4 is changed. And both of thereflection peak wavelengths of the optical waveguide layers 3 and 4 arechanged. It is therefore possible to control the lasing wavelength ofthe wavelength-tunable semiconductor laser chip 40. Accordingly, it ispossible to control the lasing wavelength of the wavelength-tunablesemiconductor laser chip 40 by controlling the current provided to theheater 9 and the temperature control device 20.

The temperature of the surface of the temperature control device 20 issubstantially equal to that of the electrode 31 provided on the mountcarrier 30, because the mount carrier 30 is mounted on the temperaturecontrol device 20. The heat generated in the temperature control device20 is thus conducted to the electrode 8 from the electrode 31 throughthe wires 32. And the heat is conducted to the optical waveguide layer 4from the electrode 8. The optical waveguide layer 4 is heated from upperside and lower side thereof. Therefore, the temperature control device20 can control the temperature of the optical waveguide layer 4 to besubstantially constant. The temperature control device 20 can controlthe temperature of the optical waveguide layer 4 effectively, being lesssubjected to the heat of the heater 9.

It is preferable that connecting points between the wires 32 and theelectrode 8 are at a substantially equal interval on the overall of theelectrode 8, because the thermal conductivity to the electrode 8 isimproved in this case. It is preferable that the number of the wire 32is larger.

In the embodiment, the wavelength-tunable semiconductor laser chip 40corresponds to the optical semiconductor element. The mount carrier 30corresponds to the area to be thermally conducted to the temperaturecontrol device. The wire 32 corresponds to the thermal conductivematerial. The SG-DFB region B corresponds to the first optical waveguideregion. The SG-DR region A corresponds to the second optical waveguideregion. The electrode 31 corresponds to the metal pattern. The areawhere the sampled diffractive grating 2 is formed in the opticalwaveguide layers 3 and 4 corresponds to the first region. The spaceregion not having the sampled diffractive grating 2 corresponds to thesecond region.

Second Embodiment

Next, a description will be given of a laser module 100 a in accordancewith a second embodiment of the present invention. FIG. 2 illustrates anoverall structure of the laser module 100 a. As shown in FIG. 2, thelaser module 100 a differs from the laser module shown in FIG. 1A andFIG. 1B in a point that a thermal conductive portion 33 is provided onthe mount carrier 30. The same components have the same referencenumerals in order to avoid a duplicated explanation.

The thermal conductive portion 33 is composed of a material having ahigh thermal conductivity. The thermal conductive portion 33 may becomposed of a conductive material or an insulating material. In theembodiment, the thermal conductive portion 33 is composed of a materialsuch as Au. The thermal conductive portion 33 is not coupled to theelectrical power supply 300. The thermal conductive portion 33 does notprovide electrical power to the electrode 8 but provides heat to theelectrode 8. The electrode 31 is coupled to the electrode 8 with atleast one wire 32. The thermal conductive portion 33 is coupled to theelectrode 8 with at least one wire 32.

In the embodiment, the heat is conducted to the electrode 8 from theelectrode 31 and the thermal conductive portion 33 through the wires 32.The temperature control device 20 can control the temperature of theoptical waveguide layer 4 effectively. The wires 32 may not provide anelectrical power to the electrode 8. The effect of the present inventionis obtained when the wire 32 conducts the heat generated in thetemperature control device 20 to the electrode 8.

In the embodiment, the thermal conductive portion 33 corresponds to themetal pattern.

Third Embodiment

Next, a description will be given of a laser module 100 b in accordancewith a third embodiment of the present invention. FIG. 3 illustrates anoverall structure of the laser module 100 b. As shown in FIG. 3, thelaser module 100 b differs from the laser module 100 shown in FIG. 1Aand FIG. 1B in a point that the electrode 31 and the wavelength-tunablesemiconductor laser chip 40 are mounted directly on the temperaturecontrol device 20 not through the mount carrier 30. The same componentshave the same reference numerals in order to avoid a duplicatedexplanation.

In the embodiment, the heat generated in the temperature control device20 is conducted directly to the wavelength-tunable semiconductor laserchip 40. Further the heat is conducted directly to the electrode 31, andis conducted to the electrode 8 through the wires 32. And thetemperature control device 20 can control the temperature of the opticalwaveguide layer 4 effectively.

Fourth Embodiment

Next, a description will be given of a laser module 100 c in accordancewith a fourth embodiment of the present invention. FIG. 4 illustrates anoverall structure of the laser module 100 c. As shown in FIG. 4, thelaser module 100 c differs from the laser module 100 shown in FIG. 1Aand FIG. 1B in a point that the electrode 31 and the wavelength-tunablesemiconductor laser chip 40 are mounted directly on the temperaturecontrol device 20 and the thermal conductive portion 33 is provided onthe temperature control device 20. The same components have the samereference numerals in order to avoid a duplicated explanation.

In the embodiment, the heat generated in the temperature control device20 is conducted directly to the wavelength-tunable semiconductor laserchip 40. Further the heat is conducted directly to the electrode 31 andthe thermal conductive portion 33, and is conducted to the electrode 8through the wires 32. And the temperature control device 20 can controlthe temperature of the optical waveguide layer 4 effectively.

Fifth Embodiment

Next, a description will be given of a laser module 100 d in accordancewith a fifth embodiment of the present invention. FIG. 5 illustrates anoverall structure of the laser module 100 d. As shown in FIG. 5, thelaser module 100 d differs from the laser module 100 a shown in FIG. 2in a point that a metal pattern 34 is provided on an upper face of theSG-DFB region B. The metal pattern 34 is electrically coupled to theoptical waveguide layer 4. The metal pattern 34 is coupled to thethermal conductive portion 33 with one or more than one wire 32. Thesame components have the same reference numerals in order to avoid aduplicated explanation.

In the embodiment, heat is conducted to the metal pattern 34 from thethermal conductive portion 33 through the wires 32. And the temperaturecontrol device 20 can control the temperature of the optical waveguidelayer 4 effectively. In the embodiment, the metal pattern 34 correspondsto the area electrically coupled to the first optical waveguide region.

Sixth Embodiment

Next, a description will be given of a laser module 100 e in accordancewith a sixth embodiment of the present invention. FIG. 6 illustrates anoverall structure of the laser module 100 e. As shown in FIG. 6, thelaser module 100 e is different from the laser module 100 shown in FIG.1A and FIG. 1B in a point that the metal pattern 34 is provided on theupper face of the SG-DFB region B and is electrically conducted to theelectrode 8. The metal pattern 34 is electrically coupled to the opticalwaveguide layer 4. The metal pattern 34 is coupled to the thermalconductive portion 33 with the wires 32. The same components have thesame reference numerals in order to avoid a duplicated explanation.

In the embodiment, the metal pattern 34 has a length larger than half ofthat of the optical waveguide layer 4 in an optical axis direction ofthe optical waveguide layer 4. It is possible to provide heat to theoptical waveguide layer 4 because the length of the metal pattern 34 issufficiently large.

Seventh Embodiment

A description will be given of a laser module 100 f in accordance with aseventh embodiment of the present invention. FIG. 7 illustrates anoverall structure of the laser module 100 f. As shown in FIG. 7, thelaser module 100 f is different from the laser module 100 e shown inFIG. 6 in a point that the metal pattern 34 is arranged at the opticalwaveguide layer 3 side with respect to a center of the optical waveguidelayer 4. The same components have the same reference numerals in orderto avoid a duplicated explanation. In this case, it is possible tocontrol the temperature of an area that is subjected to the heat fromthe heater 9.

The optical semiconductor device in accordance with the presentinvention is not limited to the SG-DR region or the SG-DFB region,although the SG-DR region and the SG-DFB region are an example of theoptical semiconductor device in the above embodiments. The presentinvention may be applied to other optical semiconductor device that hasa heater controlling a temperature of an optical waveguide layer.

FIG. 8 illustrates an example where the present invention is applied toa modulator. As shown in FIG. 8, it is possible to provide heat to anupper face of the modulator of an optical semiconductor element from aheating portion such as a temperature control device through a wire, theoptical semiconductor element having a gain portion and the modulator,the gain portion having a heater on a surface thereof, the modulator nothaving a heater on a surface thereof.

While the above description constitutes the preferred embodiments of thepresent invention, it will be appreciated that the invention issusceptible of modification, variation and change without departing fromthe proper scope and fair meaning of the accompanying claims.

The present invention is based on Japanese Patent Application No.2006-100351 filed on Mar. 31, 2006, the entire disclosure of which ishereby incorporated by reference.

1. An optical semiconductor device comprising: an optical semiconductorelement that has a first optical waveguide region and a second opticalwaveguide region, the second optical waveguide region being opticallycoupled to the first optical waveguide region and having a heater forchanging a refractive index of the second optical waveguide region; ametal pattern that is provided on an area to be thermally coupled to atemperature control device; and at least one thermal conductive materialthat couples the metal pattern with an upper face of the first opticalwaveguide region of the optical semiconductor element, the thermalconductive material being electrically separated from the first opticalwaveguide region.
 2. The optical semiconductor device as claimed inclaim 1, wherein at least one of the thermal conductive materials iscoupled to an area at the second optical waveguide region side withrespect to a center of the first optical waveguide region.
 3. Theoptical semiconductor device as claimed in claim 1, further comprising asecond metal pattern that is provided on the area to be thermallycoupled to the temperature control device and to be electrically coupledto outside, wherein the second metal pattern is electrically coupled tothe area through the thermal conductive material, the area being on anupper face of the first optical waveguide region and being electricallycoupled to the first optical waveguide region.
 4. The opticalsemiconductor device as claimed in claim 1, wherein the first opticalwaveguide region is a gain region or a modulator region.